# What am I doing wrong here? I am trying to recreate following highlighted equations in the table.

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Nissal Arachchige le 26 Mar 2021
ep = linspace(0,1);
m1 = 1.5; m2 = 3.8;
ep0= 1; alpha = 0.785; epp = 0.11;
qep = (2.76*ep*cosh((3*ep)-1.92));
I1 = ep.^ m1;
I2 = ep.^ m2;
I3 = ep*((ep-epp)/(ep0-epp)).^alpha;
I6 = 1-(qep*((3*(1-ep))/(3-ep)));
Hold on
plot(ep,I1)
plot(ep,I2)
plot(ep,I3)
plot(ep,I6)
Hold off
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### Réponse acceptée

Paul Hoffrichter le 27 Mar 2021
Modifié(e) : Paul Hoffrichter le 27 Mar 2021
clc; clear; clf
ep = linspace(0,1);
m1 = 1.5; m2 = 3.8;
ep0= 1; alpha = 0.785; epp = 0.11;
qep = (2.76*ep.*cosh((3*ep)-1.92));
I1 = ep.^ m1;
I2 = ep.^ m2;
zz = (ep-epp)/(ep0-epp);
zza = zz .^ alpha; % zza is complex
I3 = ep .* zza;
I6 = 1-(qep*((3*(1-ep))/(3-ep)));
hold on
plot(ep,I1);
plot(ep,I2)
plot(ep,I3) % This is Line 18 - usually do not plot a complex vector like this
plot(ep,I6)
hold off
warning:
Warning: Imaginary parts of complex X and/or Y arguments ignored.
> In Untitled (line 18)
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Nissal Arachchige le 27 Mar 2021
No not at all. I was actually able to recognize my coading problem before you posted the answer and I got the same solution as you and the warning as well. I do not know why it does that. And I was supposed to recreate the follwing graph but ignore the points and the legend. I'm waiting for the feedback from my professor. I'll let you know if something intresting come up. Thanks again.
Paul Hoffrichter le 28 Mar 2021
I was a surprised at first about the complex numbers. But then I thought about what if alpha was 0.5 instead of 0.785. Then if x is a negative number, we have a purely imaginary result for x^(.5)=sqrt(x)= sqrt{(-1) * abs(x)} = 0 + j*sqrt(abs(x)). For other values of alpha between (0.5, 1.0), we get complex numbers.

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